Vinegar burns what you spray and nothing past that. A vinegar weed killer browns the leaves you wet, often within a few hours on a hot afternoon, while the roots sit untouched under your soil. Young seedlings do die. Anything holding an established crown pushes fresh leaves again, so the fast brown-off you see stops at the soil line.
From the kitchen window my own side yard slopes away toward the fence, and the morning after I sprayed, the whole strip had gone the color of wet cardboard. Brown, limp, flat against the gravel. By the second week I noticed green shoots pushing through that brown mat, thicker along the fence line than before. I pulled one dandelion and the root came up as thick as a pencil, white and firm the whole way down. The lawn grass caught by the same mist stayed pale all summer.
A contact killer destroys only the tissue you wet. An acetic acid herbicide kills the leaf cells your droplets land on, and nothing travels down the stem to the root. A young annual has no reserves to fall back on, so one good soaking finishes that plant for good. A perennial keeps a crown or a rhizome below the spray line and rebuilds from there, no matter how brown you make the top.
University of Maryland Extension groups acetic acid with clove, cinnamon and rosemary oils. Chelated iron, potassium salts of fatty acids and corn gluten sit in the same list. So does d-limonene, the orange oil active. Every one is non-selective and contact only. The word organic on the jug tells you where the active came from, and nothing more. Depth is what decides whether your weed comes back.
Every green thing your mist lands on browns, including lawn grass, seedlings in the next bed and the low leaves of a shrub. Keep the nozzle low and shield anything you want to keep.
Speed of kill runs from quick to more than a week, depending on the active you buy. A vinegar weed killer that browns in an hour is doing no deeper work than a slower product. Compare either with glyphosate, which moves through the plant and blocks an enzyme the plant needs. Death takes 4 to 20 days there, and the slow look you get is the roots dying with the leaves.
- Spray young: Hit seedlings while your weeds are growing hard. A mature, hardened weed barely reacts to a surface burn.
- Skip stressed ground: Leave drought-stressed turf and beds alone until you see recovery, because a shut-down plant takes up almost nothing you spray.
- Cut first: Cutting weeds back a few days before you spray lowers the amount of product your job needs.
- Shield the keepers: Hold a piece of cardboard between your nozzle and any grass, hosta or hedge you want green.
- Pull perennial roots by hand instead of spraying the same crown a fourth time.
An organic weed spray earns a place in driveway cracks, along a gravel path and in the gap under your fence. Spray young growth only, and only where your label lists the site you are treating. Read that part before you buy. A product cleared for a patio may say nothing about your vegetable bed, and the site list is the line most people skip.
Plan on repeat passes instead of one heroic afternoon. Two or three trips over the same patch in a season is normal, and a vinegar weed killer buys you a clean look for a few weeks at a time. When a crown keeps coming back, get a hand weeder under it and lift the root out whole. Hand-weeding still does the job no contact product can do for you.
Read the full article: How to Choose a Weed Killer That Actually Works
